I got this idea late last night so its just an hypothetical idea
how to get shoot to zig zaging enemy...
Assumptions:
1. I think computers zig zag is symmetrical in pattern?
2. Computer zig zags in line with its original course?
Result:
1. If we know targets course and its "relative speed" (speed target actually travels) like 6 knts
2. We can calculate its "true speed" (distance/time seen from u-boat number 1.) something like 4 knts
3. AND adjust our torp speed to that "true speed".
As you can see this is just very raw idea, and you are free to
prove it all wrong...
(Actually I just wanted to show how good I´m with paint

)